Good thing bad thing

[down_home]

We all know not to run a vent fan when flushing the toilet..unless a window is open and maybe not then.
We've encountered some sewer systems wit a positive air pressure, usually those that are just tanks that have t be pumped every little bit.
We are on a normal hookup with n problems. The pipes etc are all good.
Never notice this before but with the vent fan on and gray tank open we were getting sewer smell. Hadn't been leaving a window partially open because it had been rather cold.
Nice to know the coach pert neer air tight...but gonna have a window a bit even if it is raining cat and dogs.

[WTP-GC]

Let’s offer some correction to the language used here:
Running the vent fan while flushing the toilet MIGHT cause odors to be drawn into the camper.
The AAV can fail and MIGHT cause odors to be drawn in.

Too many factors at play to use the word “WILL” when describing these situations.

In my case...
During warmer weather, as the black tank fills and there’s relatively stagnant air (no wind outside), odors can become more prevalent when flushing the toilet. A proper functioning vent relies in some part on having a little bit of air circulation. Kinda like how a chimney may not properly exit the smoke if it’s not above the ridge line of the roof.

[Ron3rd]

ScottG wrote:
If you want one that will last and don't mind paying a few extra bucks for it, "Sioux Chief" or "Studor" are the brands of choice.
Anything else is junk in comparison.

X2 on Studor, they have a stainless steel valve and cost around $15 and are white in color. The cheap black ones costing around $7 have a rubber flapper valve. Replace them one time with Studor

[CavemanCharlie]

rvshrinker wrote:
Is this a well documented real hazard? I mean, air goes out the kitchen vent whenever it is turned on; and presumably some air can come in as well. A hint of air can come in from around the doors, and maybe from around the slide seals.

I don’t see a lot about this on google, and we’ve run the vent plenty without opening any windows.

You’re saying if I get a hint of eau de toilette I’ve somehow overcome the valve described above? Or the water trap itself?

OK, I think what is going on here is that you have a RV toilet that has a water trap. Like a house toilet does. A lot of RV toilets have no trap and when you flush them you are just sliding open a door on the bottom of the toilet that lets the waste fall directly into the holding tank. If you have that type of toilet and you are running the exhaust fan while flushing it will draw air out of the holding tank and cause a smell in the RV.

[opnspaces]

Yes check or replace your air admittance valves.
Link to valve

The valve breaks vacuum when the sink is shut off so the tank doesn't siphon out the trap. Look under the sink and there should be a vertical spur sticking up off the drain pipe. Unscrew it and see if the flapper works in one direction only. (air flowing into tank only) If it's bad you can get a new one for a few dollars at Home Depot. Just unscrew the old one and replace

[opnspaces]

rvshrinker wrote:
What does exhaust mode mean? My fan has an on-off switch only.

How would air get sucked from the black tank to the toilet? There s no suction created; at least in my bathroom there is a gap at the top and bottom of the door to prevent moisture buildup.

This doesn’t make any sense to me.

There's a vent pipe from the tank up to the roof. My trailer also has the gap at the top and bottom of the door. But the factory supplied fan is so powerful that it creates a low pressure situation in the trailer. In fact you can easily hear the fan speed up if someone opens the main trailer door while the fan is running. If you flush with the trailer closed up like first thing in the morning while everybody is asleep;The fan will pull air down the vent pipe and across the puddle of sewage in the tank and up through the toilet around your legs. Believe me it's not a mistake you're likely to make twice.

[rvshrinker]

Is this a well documented real hazard? I mean, air goes out the kitchen vent whenever it is turned on; and presumably some air can come in as well. A hint of air can come in from around the doors, and maybe from around the slide seals.

I don’t see a lot about this on google, and we’ve run the vent plenty without opening any windows.

You’re saying if I get a hint of eau de toilette I’ve somehow overcome the valve described above? Or the water trap itself?

[Lynnmor]

rvshrinker wrote:
What does exhaust mode mean? My fan has an on-off switch only.

How would air get sucked from the black tank to the toilet? There s no suction created; at least in my bathroom there is a gap at the top and bottom of the door to prevent moisture buildup.

This doesn’t make any sense to me.

If air is blowing out of the trailer, it must come in somewhere. Open a window or open the toilet, your choice.

[rvshrinker]

What does exhaust mode mean? My fan has an on-off switch only.

How would air get sucked from the black tank to the toilet? There s no suction created; at least in my bathroom there is a gap at the top and bottom of the door to prevent moisture buildup.

This doesn’t make any sense to me.

[mobeewan]

rvshrinker wrote:
What is the OP Talking about? What does the fan vent have to do with flushing the loo?

If you are running the bathroom vent fan in exhaust mode and flush the toilet, air from the black tank will get sucked into the trailer making for a stinky situation inside the trailer.

[rvshrinker]

What is the OP Talking about? What does the fan vent have to do with flushing the loo?

[Lynnmor]

Try Google

rvshrinker wrote:
I have no idea what you all are talking about. Can you explain?

[rvshrinker]

I have no idea what you all are talking about. Can you explain?

[ScottG]

If you want one that will last and don't mind paying a few extra bucks for it, "Sioux Chief" or "Studor" are the brands of choice.
Anything else is junk in comparison.

[rockylarson]

Air Admittance valve CLICKY

This is OEM under my sinks in both bath and kitchen. I stayed with it because of limited clearance above the valve. I change them out at the slightest hint of odor.

Amazon has many levels of quality and design. ACE,HD,Lowes,Menards,Canadian Tire and the like.

They are designed to let air into the drain pipes when you open your sewer lines to dump. If they were not there the vacuum would suck out the protective water seal in the "P" traps.

I don't recommend Leaving the grey sewer open until ready to dump.